The Python List is one of the most useful sequences in real-time. A Python list is a sequence of multiple values in an ordered sequence. Unlike Strings, Python List allows us to store different types of data such as integer, float, string, etc.
Declare Python Lists
There are several ways to create a List in Python. The most straightforward way is to place the required list items within a square bracket [ ]. A list that contains no values or elements is an empty list. By placing an empty square bracket create an empty list.
List_Name = []
The first statement is an integer list of five integer values. The second statement is a string list that contains three String values or three words.
Integer_List = [1, 2, 3, 4, 5] String_List = ['apple', 'Orange', 'Grape', 'Mango']
Python lists allow placing different data types in a single list. It is an example of a mixed list, which contains one integer, float, and two integer values.
Mixed_List = ['apple', 2, 3.50, 'Mango']
How to access Python List items?
Lists sequentially store data (ordered list). So, we can access the list elements with the help of indexes. Moreover, using indexes, we can access or alter/change each item present in the Lists separately. The syntax to access List items is
List_Name([Index_Number])
Index value starts at 0 and ends at n-1, where n is the list size. For example, if a list stores 5 elements, the index starts at 0 and ends with 4. To access or alter the first list value, use list_name[0], and to access the fifth list item, use list_name[4]. Let’s see the list example for better understanding:
x = [1, 2, 3, 4, 5, 6, 7, 8, 9]
# Positive Indexing
print(x[0])
print(x[4])
print(x[8])
print('=======\n')
# Negative Indexing
print(x[-2])
print(x[-4])
print(x[-8])
Please use Negative numbers as the list index to access list items from right to left. It means access list items in reverse order.
# How to Access List Items
x = ['apple', 'Mango', 'banana', 'orange', 'cherry','kiwi']
# List Items using Positive Index
print("List Item at Index Position 0 = ", x[0])
print("List Item at Index Position 2 = ", x[2])
print("List Item at Index Position 4 = ", x[4])
print("List Item at Index Position 3 = ", x[3])
print('=======\n')
# List Items using Negative Index
print("List Item at Index Position -1 = ", x[-1])
print("List Item at Index Position -3 = ", x[-3])
print("List Item at Index Position -5 = ", x[-5])
print("List Item at Index Position -6 = ", x[-6])
Alter Python List Items
Since Lists are mutable, apart from accessing items, use this index positions to alter or replace the list items.
Iterate Python List items
A For Loop is the most common way to traverse the list items. It helps to iterate the list and print the items inside the list. This code works accurately to print items inside the list. However, to alter the individual list item, we need the index position. To resolve this, we have to use the Python range function along with Python for loop.
Fruits = ['Apple', 'Orange', 'Grape', 'Banana']
for Fruit in Fruits:
print(Fruit)
It multiplies each item with 10. If we want to perform the calculation based on condition, then use Python If Statement inside the for loop.
# Altering List using range
x = [1, 2, 3, 4, 5, 6, 7, 8, 9]
for Number in range(len(x)):
x[Number] = x[Number] * 10
print(x)
In this example, we declared a String list.
- The first for loop is to iterate and print the list items.
- The second for loop, along with the range, to iterate each list item using the position of an index.
Let us see another list example.
# Iterate List Items
Fruits = ['apple', 'Mango', 'banana', 'orange', 'cherry','kiwi']
# Iterate List Items
for fruit in Fruits:
print(fruit)
# Iterate List Items using Index
for i in range(len(Fruits)):
print("List Item at Index Position", i, " = ", Fruits[i])
Insert items into List
The list of available options to insert new items into the existing list in Python
- Append(x): Adds item x at the end of the list.
- Insert(i, x): it inserts the specified list item x at index position i.
- Extend(New_List): Adds all the list items in New_List at the end of the list.
Fruits = ['Apple', 'Orange', 'Grape', 'Banana']
# Adding items using Python append
Fruits.append('Blackberry')
print(Fruits)
# inserting items using Python insert
Fruits.insert(2, 'Kiwi')
print(Fruits)
# Extending List using Python extend
Fruit_new = ['berry','Cherry']
Fruits.extend(Fruit_new)
print(Fruits)
Python List Slicing
In python Slice, the first integer value is the index position where the slicing start and the second integer value is the index position where the slicing end. List Slicing in Python go untill the second integer value but not include the value at this end index position. For instance, if we specify a list[1:4], then list slicing start at index position one and end at 3 (not 4)
# List slicing
x = [1, 2, 3, 4, 5, 6, 7, 8, 9]
# Slicing List using two indexes
a = x[2:6]
print("Both Indexes = ", a)
# Slicing List using First indexes
b = x[:6]
print("No First Index = ", b)
# Slicing List using Second indexes
c = x[2:]
print("No Second Index = ", c)
# Slicing List without using two indexes
d = x[:]
print("No Indexes = ", d)
Use Negative numbers as the index values to slice the list items.
# List slicing
x = [1, 2, 3, 4, 5, 6, 7, 8, 9]
# Slicing List using Negative indexes
e = x[-3:]
print("Negative First Index = ", e)
# Slicing List using Negative indexes
f = x[:-2]
print("Negative Second Index = ", f)
# Slicing List using Negative indexes
g = x[-7:-2]
print("Negative First and Second Index = ", g)
# Assigning new values to a List
x[1:3] = ['t','g']
print("After altering = ", x)
From the above List slicing
- Omit the first index means the Python List Slicing start from the beginning.
- Omit the second index, List slicing start from the first index and continue to the last.
- Use the Negative values to Slice the list items from right to left.
Remove Python List items
There are several ways to delete items from a Lists:
List remove method
If we know the List item or the value inside the List, then use the remove method to remove the list item.
- We are removing the Grape item from the Fruit1 and displaying the remaining list.
- Removed the Orange item from the Fruit2. We have two Orange items in this list, but the remove method removed only one item. It is because the remove method only deletes the first instance of the list item and ignores the remaining.
- We removed the nonexisting item. That is why it is throwing an error saying x is not in the list.
# Removing Grape Item from Fruit List
Fruit1 = ['Apple', 'Orange', 'Grape', 'Banana']
Fruit1.remove('Grape')
print(Fruit1)
print('========')
# Removing Orange Item from Fruits List
Fruit2 = ['Apple', 'Orange', 'Grape', 'Banana', 'Orange']
Fruit2.remove('Orange')
print(Fruit2)
print('========')
# Removing Non Existing Grape Item from Fruits1 List
Fruit3 = ['Apple', 'Orange', 'Banana']
Fruit3.remove('Grape')
print(Fruit3)
Python List del statement
The Delete function removes the list value at a specified index. After deleting, remaining values moved up to fill the index gap. If we know the Index value or want to delete a range of items from the given list, then use del statement to remove the list item.
- We are deleting an item at index position 1, which is Orange. After deleting the Orange, the index position of Grape automatically become one and Banana as 2.
- We deleted an item at index position 1, which is Grape.
- Within the Fourth list, we removed the non-existing list item. That is why it throws an error saying index out of range.
# List Delete example
Fruits = ['Apple', 'Orange', 'Grape', 'Banana']
del Fruits[1]
print(Fruits)
print('========')
del Fruits[1]
print(Fruits)
print('========')
del Fruits[1]
print(Fruits)
print('========')
del Fruits[1]
print(Fruits)
Removing Python List items using pop method
The list pop method removes the list items at the specified index and displays the removed element. After removing, remaining list values move up to fill the index gap. If we know the Index value and want to see the deleted value, we can use python pop to remove the list item.
# List Pop Method example
Fruits = ['Apple', 'Orange', 'Grape', 'Banana']
Fruit = Fruits.pop(1)
print(Fruits)
print('Item extracted by Python Pop = ', Fruit)
print('========')
Fruit = Fruits.pop(1)
print(Fruits)
print('Item extracted by Python Pop = ', Fruit)
print('========')
Fruit = Fruits.pop(1)
print(Fruits)
print('Item extracted by Python Pop = ', Fruit)
print('========')
Python List Methods
The list of available methods to perform operations on python list:
Python list copy
List Copy method shallow copy the list items into a completely new list.
# Python List copy
Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
numbers = [9, 4, -5, 0, 22, -1, 2, 14]
print("Original List : ", Fruits)
print("Original number List : ", numbers)
#Copying the List using Python Copy() Method
New_Fruits = Fruits.copy()
print("\nNew List : ", New_Fruits)
new_numbers = numbers.copy()
print("New Number List : ", new_numbers)
Python list clear
List clear method clears all the existing list items. After executing this clear method, it returns an empty list.
# Python List clear
Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
numbers = [9, 4, -5, 0, 22, -1, 2, 14]
print("Original List : ", Fruits)
print("Original number List : ", numbers)
#Clear the List using Python Clear() Method
New_Fruits = Fruits.clear()
print("\nNew List : ", New_Fruits)
new_numbers = numbers.clear()
print("New Number List : ", new_numbers)
Python list sort
List sort method sorts the list items in the Ascending order.
# Python List sort
Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
numbers = [9, 4, -5, 0, 22, -1, 2, 14]
print("Original List : ", Fruits)
print("Original number List : ", numbers)
#Sort the List using Python sort() Method
Fruits.sort()
print("\nSorted List : ", Fruits)
numbers.sort()
print("New Sorted Number List : ", numbers)
Python list reverse
The list reverse method reverses the list items.
# Python List reverse
Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
numbers = [9, 4, -5, 0, 22, -1, 2, 14]
print("Original List : ", Fruits)
print("Original number List : ", numbers)
#Reverse the List using Python reverse() Method
Fruits.reverse()
print("\nReverse List : ", Fruits)
numbers.reverse()
print("New Reverse Number List : ", numbers)
list index
Python List index function returns the index position of a value in a list.
# Python List index
Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
numbers = [9, 4, -5, 0, 22, -1, 2, 14]
print("Original List : ", Fruits)
print("Original number List : ", numbers)
#Index of List items using Python index() Method
print('The Index position of Kiwi = ', Fruits.index('Kiwi'))
print('The Index position of Orange = ', Fruits.index('Orange'))
print('The Index position of Grape = ', Fruits.index('Grape'))
print('The Index position of 0 = ', numbers.index(0))
print('The Index position of 2 = ', numbers.index(2))
print('The Index position of -1 = ', numbers.index(-1))
Python list count
The List count function counts the number of times a value repeated inside the list.
# Python List count
Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Apple', 'Kiwi']
numbers = [9, 4, -5, 0, 9, -1, 4, 9]
print("Original List : ", Fruits)
#Count of List items using Python count() Method
print('Number of Times Kiwi is repeated = ', Fruits.count('Kiwi'))
print('Number of Times Apple is repeated = ', Fruits.count('Apple'))
print('Number of Times Banana is repeated ', Fruits.count('Banana'))
print("\nOriginal number List : ", numbers)
print('Number of Times 9 is repeated = ', numbers.count(9))
print('Number of Times 4 is repeated = ', numbers.count(4))
print('Number of Times 0 is repeated = ', numbers.count(0))
In this Python Lists program, we are applying all the list methods.
Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
x = [9, 4, -5, 0, 22, -1, 2, 14]
#Copying the List using Python Copy() Method
New_Fruits = Fruits.copy()
print(New_Fruits)
#Removing all the List items using Python Clear() Method
New_Fruits.clear()
print(New_Fruits)
# Sorting the List using Python Sort() Method
Fruits.sort()
x.sort()
print(Fruits)
print(x)
# Reverse the List using Python reverse() Method
Fruits.reverse()
x.reverse()
print(Fruits)
print(x)
# Index position of an item in the List using Python index() Method
print('The Index position of Banana = ', Fruits.index('Banana'))
print('The Index position of -1 = ', x.index(-1))
# Counting items in the List using Python count() Method
y = [9, 4, 1, 4, 9, -1, 2, 4]
print('Number of Times 4 is repeated = ', y.count(4))
print('Number of Times 9 is repeated = ', y.count(9))
List sum
The Python List sum function finds the sum of all items.
# Python List sum
int_list = [5, 10, 15, 20, 25]
print("List Items : ", int_list)
# sum of list elements
total = sum(int_list)
print("\nThe sum of total items in this list = ", total)
List min and max function
The List min function finds the minimum value.
# Python List min
int_list = [50, 10, 150, 20, 205, 500, 7, 25, 175]
print("List Items : ", int_list)
# Minimum list element
minimum = min(int_list)
print("\nThe Minimum item in this list = ", minimum)
The List max function finds the maximum value.
# Python List max
int_list = [50, 10, 150, 20, 205, 500, 7, 25, 175]
print("List Items : ", int_list)
# Maximum list element
maximum = max(int_list)
print("\nThe Maximum item in this list = ", maximum)
Python List Arithmetic Operations Example
Using the Arithmetic Operators on Lists to perform arithmetic operations.
- + operator is concatenating the Lists.
- * operator is repeating the list for a given number of times. Here it is three times.
# Python List count
x = [10, 20, 30, 40]
y = [15, 25, 35, 45]
# using + Operator
total = x + y
print("\nAddition : ", total)
# using * Operator
multi = x * 2
print("Multiplication : ", multi)
multi2 = y * 3
print("Multiplication of Y : ", multi2)
